The storm drains here were built in the 1970s for less rain and less pavement than the neighborhood has today. A computer model of all 80 acres shows where water backs up onto streets in heavy storms, and tests three fixes. Together they cut street flooding by about 40% and bring the stream’s peak flow down sharply in the storms that happen every few years.
Ponds 11161/27293 and 11178 are dug out about 50% wider, their berms raised 2 feet, and their outlets rebuilt. Together they hold 5.1 acre-feet instead of 2.1. That is about 1.7 million gallons, released slowly instead of all at once.
The main line on the west side carries runoff from about 27 acres. Ten pipe sections go from 21–36 inches to 24–42 inches, sized for the heavier 10-year storms expected by 2050. This is what clears water off the streets.
The townhouse parking courts make up 12 of the area’s 33 paved acres. Rain gardens using about 6% of that space (0.7 acres) soak up and filter the first inch of rain. That covers most everyday storms and most of the pollution they carry.
Each fix alone solves one problem and leaves the other. A bigger pipe alone clears the streets but sends 13% more water at the stream in a 100-year storm. Bigger ponds alone protect the stream but leave the streets flooding. Built together, they do both.
Built in EPA SWMM 5.2 from public data: Montgomery County’s storm drain inventory and pond records, 2023 USGS LiDAR elevation, 2023 county planimetric maps of pavement and roofs, and USDA soils. Storms use Montgomery County’s rainfall depths for today and for 2050. Checked against the original 1970s design plans: modeled flows in the main pipe run about 20% above what it was designed for.
Pond outlet structures and a dozen pipe sizes are not in public records and were estimated. This is an illustrative planning study by Neelon Engineering Solutions, not a sealed engineering design.
© 2026 Amin Ilia and Neelon Engineering Solutions LLC. All rights reserved. No part of this study, its maps, figures or model may be copied or reused without written permission.
Basemap drawn from M-NCPPC Impervious 2023 and USGS 3DEP; street names from the Montgomery County street centerline. Map units: Maryland State Plane, feet.